Changing LAS Class Codes to numbers above 255

Question

I have a fully classified lidar of a substation.  It is classified the with regular codes (2 = Ground, 6= Building)

The issue is I need to change the codes to numbers that are going to be higher than 255 (275 = Building)

Does ArcPro have a way to do this?

Khalid · Answer

Apologies for the belated reply.  It is not possible to assign numbers outside the range of 0 to 255 because the LAS format does not support classification values beyond this range. For reference, you can review the LAS specifications on the ASPRS website here:
https://community.asprs.org/leadership-restricted/leadership-content/public-documents/standards

With your substation data, you mentioned needing a way to reassign buildings to a value outside the range of 0 to 255.  It would be best to consider leaving the buildings as class 6 so that they can be handled in a predictable way by other operations that honor this designation.  For example, our building classifier is designed to work with the LAS specification, and it would assign building points as class 6.  If the class assigned to buildings is changed to something else, then it would require constant management if a tool or operation that uses class 6 is being leveraged to manage such data.

The LAS specifications divide class codes into two categories- "Reserved" and "User Definable". The reserved category represents classes 0 to 63, and their meaning is either predefined (e.g. 2 for ground, 6 for building and so on) or will be defined in the future by the ASPRS. The "user definable" classes are 64 to 255, and they are intended to support the need for classifying objects that are not accounted for by the ASPRS.

The ASPRS advises that any classes that are already defined in the "reserved" portion should be consistently used in all LAS files, and that any classes that are not defined should be assigned a value in the "user definable" portion.  Below is the relevant portion from the LAS format specifications:

LAS Classification Information

It would be helpful to get a better sense about your classification objectives to see if there is a way to align it with the LAS specifications.  I have heard on several occasions that LAS classification in electric utility management often exhausts the range of classes supported by LAS files, and would greatly appreciate any insight you can share about your desired objectives for classifying your lidar.

Perhaps one solution could be to advocate for an officially recognized domain profile for electric utility related lidar that could entail the incorporation of "extra bytes" to store additional attributes that contain secondary classification details.  In this approach, the class code attribute could be used as a primary classifier (e.g. 14 for conductor line) and the extra byte can be used to store another integer whose meaning further clarifies what type of conductor line is identified (e.g. class 14 - extra byte 0 = low voltage line, extra byte 1 = high voltage in a particular range, and extra byte 2 =  high voltage in a different range, and so on).

Another more immediate approach may be to leverage the attribute called "user data" as a secondary class code in the same manner described above.  User data is an integer attribute that supports values in the range of 0 to 255, and it does not have any particular meaning, but can be used to represent any information desired by the user. This could also offer a potential solution for storing secondary classification information.

Regardless, it would be great to hear more about your needs for extra classes.

ScottWagoner1 · Answer

Sorry, I read that documentation.  It only allows you to change the code if the new code is 255 or smaller. If the code number needed to change is above 255 the tool fails.

Is there a way in pro to do this, or any other program you would suggest.

DanPatterson · Answer

Change LAS Class Codes (3D Analyst)—ArcGIS Pro | Documentation

Edit LAS file classification codes—ArcGIS Pro | Documentation

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